The use of buffered and microbiological growth media for microbiological assays is widespread. To obtain accurate assays, it is important that the volume of the fluid be exact to obtain proper dilution of, for example, a bacteria-containing sample, and of paramount importance that its sterility is ensured. It is also important that the concentration of the buffer or growth media components have a predetermined known value. This may be achieved by the preparation of fresh batches of the assay fluids, measuring and/or adjusting the concentration of the components, then using the assay fluids promptly thereafter. The chief drawback of this approach is that it is both time-consuming, labor-intensive and subjects the assay fluid to the possible introduction of sterility-destroying microorganisms.
An alternative, simpler approach has been to use premade sterile microbiological assay fluids that come in specific volumes and concentrations. However, in order to maintain sterility and the proper volume and concentration during storage and shipping, such premade fluids must be contained in fluid-tight containers that prevent the entry of microorganisms and that permit essentially no loss of fluid either through leakage or evaporation. This may be achieved by the use of a container having, for example, a molded breakable seal formed essentially integrally with the container's opening. The drawback of such an approach is that, once the seal is broken, the fluid must be used immediately and any remainder discarded.
The achievement of absolutely fluid-tight reusable containers has been difficult, with even the most fluid-tight containers exhibiting leakage when they are shipped by air, where the lower atmospheric pressure existing at high altitudes, coupled with a lowered vapor pressure of the fluid combine to create a higher relative pressure inside the container, thereby tending to force the liquid out of the container.
There is therefore a need in the art for a fluid-tight container that exhibits essentially no loss of fluid during storage and shipping, including shipment by air, that remains sterile until it is used and that, once opened, may again be sealed to maintain sterility and the predetermined volume and concentration of the assay fluid's components, and which permits retesting of the assay fluid in a simple and convenient manner.
The foregoing need is met by the present invention, which is summarized and described in detail below.